Projection type display apparatus

ABSTRACT

A projection type display apparatus that projects video onto a screen includes a liquid crystal panel using polymer-dispersed liquid crystal that disperses light when a voltage is applied and that transmits light when a voltage is not applied, being attached to an apparatus body  2  as a screen  1 ; and the video output from the apparatus body  2  is projected onto the screen  1  from the front side. Accordingly, there is provided the projection type display apparatus suitable for use in small space such as at home, in which a place for setting the apparatus is flexibly selected and the feeling of oppression is mitigated when the apparatus is not used.

TECHNICAL FIELD

The present invention relates to a projection type display apparatus,particularly, to the apparatus suitable for use in comparatively smallspace such as at home.

BACKGROUND ART

A projection type display apparatus such as a liquid crystal projectoror the like has been widely used as a video display apparatus having alarge-sized screen.

There have been known conventional projection type display apparatuses,one of which is classified as a front type (front projection type) inwhich from the front surface video is projected onto a reflective typescreen provided separately from a projection type display apparatus, andthe other of which is a rear type (rear projection type) in which fromthe rear surface video is projected onto a transmissive type screenintegrally provided with a projection type display apparatus.

Conventionally, when a front projection type display apparatus is set athome, in general, a reflective screen is attached on a wall in a livingroom or the like and the front projection type display apparatus is setat the position where video can be projected onto this reflectivescreen.

Also, a conventional rear projection type display apparatus contains allparts of the light pass from a projection lens to a transmissive screenin a housing thereof, so that the apparatus has a large-sized box shape(for example, several ten centimeters in depth and about one meter inboth the length and the width). As a result, a conventional rearprojection type display apparatus is set at a corner or the like of aliving room at home, in general.

Further, at home due to the limitation of a size of wall where suchreflective screen can be attached, a place for setting a conventionalfront projection type display apparatus may not freely selected at home.

Furthermore, in case that a reflective type screen is attached on a wallat home, when video is not projected on the screen (at the time when thefront projection type display apparatus is not used), due toconspicuousness of this screen the feeling of uncomfortable oppressionis given to the living environment.

Also, regarding a conventional large-sized rear projection type displayapparatus, there isn't much choice on a place where the apparatus can beset at home and the feeling of uncomfortable oppression is given to theliving environment when the apparatus is not used.

In light of the above, the present invention is to provide a projectiontype display apparatus suitable for use in a comparatively small spacesuch as at home, in which a place for setting the apparatus is morefreely selected and a feeling of oppression is mitigated when theapparatus is not used.

DISCLOSURE OF THE INVENTION

In order to solve the above problems, applicants of the presentinvention provide a projection type display apparatus that projectsvideo onto a screen, in which a liquid crystal panel usingpolymer-dispersed liquid crystal that disperses light when a voltage isapplied thereto and that transmits light when a voltage is not appliedthereto is attached as a screen to a body of apparatus and the videooutput from the apparatus is projected onto the screen from the front.

This projection type display apparatus is a front projection typedisplay apparatus in which video is projected onto a screen attached toan apparatus body (the apparatus itself and the screen are integrallyprovided) Therefore, it is not necessary to attach a screen on a wall orthe like at home, contrary to a conventional front projection typedisplay apparatus. Also, it is not necessary to contain the light passfrom the projection lens to a screen in a housing, contrary to aconventional rear projection type display apparatus, so that theapparatus can be small-sized. Accordingly, even if the apparatus is setin comparatively narrow space such as at home, a place for setting theapparatus can be more freely selected.

Further, in this projection type display apparatus a screen consists ofa liquid crystal panel using polymer-dispersed liquid crystal. Thisscreen is made to be a light-dispersing state (opaque) capable ofprojecting video and is made to be light-transmitting state(transparent) capable of being inconspicuous when video is not projected(when the projection type display apparatus is not used). Accordingly,the screen is not conspicuous, contrary to a conventional projectiontype display apparatus, when the apparatus is not used. Further, asdescribed above, this projection type display apparatus can be smallerthan a rear projection type display apparatus. Thus, even if theapparatus is used in comparatively narrow space such as at home, afeeling of uncomfortable oppression shall not be given when theapparatus is not used.

Further, a liquid crystal panel constituting the screen employspolymer-dispersed liquid crystal that disperses light when a voltage isapplied, and that transmits light when a voltage is not applied.Therefore, when video is not projected, the screen can be transparentwithout applying a voltage, so that a consumption of a standby power canbe reduced when not used.

Moreover, in this projection type display apparatus, it is suitable forfurther providing, for example, an adjustment means for adjusting a sizeof video projected onto a screen and a control means for controlling theadjustment means in accordance with an aspect ratio of the video to beprojected.

On a screen having a predetermined shape, an area where the video is notprojected is changed depending on an aspect ratio of the video to beprojected. Therefore, by adjusting the size of video that is projectedonto a screen in accordance with the aspect ratio, video having variousaspect ratios can be projected onto a screen of a predetermined shape ata maximum angle of view, respectively.

Moreover, in this projection type display apparatus, it is suitable forfurther providing: a judgment means for distinguishing an aspect ratioof the video projected by the input video signal and a control means forcontrolling the adjustment means by this judgment means in accordancewith the aspect ratio distinguished by the judgment means.

Further, in this projection type display apparatus, it is suitable forproviding an elliptical-shaped screen.

In this projection type display apparatus, since a screen becomestransparent when not used, a user's awareness of the screen becomeslower. Then, by making a screen elliptical in shape, the safety can beenhanced when not used (even if a user touches a screen without notice,a user can not be injured because of no-corners therein).

Further, in case a screen is made elliptical-shaped as described above,an area where the video is not projected occurs surrounding a squareshaped area where the video is projected. In addition, the area withoutprojected video is changed according to an aspect ratio of the projectedvideo. Then, when an aspect ratio of the projected video isdistinguished and the size video projected onto a screen is adjusted inaccordance with this aspect ratio, video having various aspect ratioscan be projected onto an elliptical screen at a maximum angle of view,respectively.

Furthermore, for example, a screen is more suitable to have an eclipticshape in which the ratio of a major axis to a minor axis isapproximately 1.3 to 1.7. Within the range, conventional video havingvarious aspect ratios (video of NTSC/PAL system with an aspect ratio of4:3, video of Hi-Vision system with an aspect ratio of 16:9, video ofCinemascope and so on) can be projected with a minimum percentage ofunused area where none of those videos are projected in anelliptical-shaped screen.

Further, in this projection type display apparatus, for example, anelectrode is provided with a liquid crystal panel constituting a screenso that the area where video is projected is distinguished from the areawhere video is not projected, and when video is projected, it issuitable for light to be dispersed only in the area where video isprojected of a liquid crystal panel by means of an electrode voltagecontrol means that controls a voltage applied to this electrode.

Accordingly, when video is projected, the area where the video is notprojected at a screen becomes a light-transmitting state (transparent).Therefore, the video can be displayed as floating in the air (withoutmaking a user conscious of the presence of the screen).

Next, the applicants of the present invention provide a projection typedisplay apparatus which projects video onto a screen, including: aliquid crystal panel using polymer-dispersed liquid crystal that isattached to a body of apparatus as a screen, and an adjustment means foradjusting the size of video projected onto the screen and a controlmeans for controlling the adjustment means in accordance with an aspectratio of the projected video.

This projection type display apparatus is a front projection typedisplay apparatus in which video is projected onto a screen attached toa body of an apparatus from the front (namely, a body of apparatus and ascreen are integrally provided). Thus, it is not necessary to attach ascreen on a wall or the like at home, contrary to a conventional frontprojection type display apparatus. Further, it is not necessary tocontain the part of optical pass from a projection lens to a screen inthe housing contrary to a conventional rear projection type displayapparatus, so that the apparatus can be small-sized. With this, a placefor setting the apparatus can be selected more freely, even if it is setin a comparatively narrow space such as at home.

Further, in this projection type display apparatus a screen consists ofa liquid crystal panel using polymer-dispersed liquid crystal. Onto thisscreen, video can be projected in the state in which light is dispersed(opaque), and on the contrary the screen is made to be inconspicuous inthe state in which light is transmitted (transparent), when video is notprojected (when the projection type display apparatus is not used).Thus, a screen is not conspicuous when not used, contrary to aconventional projection type display apparatus. Further, as describedabove, this projection type display apparatus can be small-sized than arear projection type display apparatus. Accordingly, a feeling ofuncomfortable oppression is not given, even in a comparatively smallspace such as at home when not used.

Further, on a screen of predetermined shape, an area where video is notprojected changes depending on an aspect ratio of projected video;however, by adjusting the size of the video projected onto a screen inaccordance with this aspect ratio, video having various aspect ratioscan be projected at a maximum angle of view onto the screen having apredetermined shape, respectively.

Furthermore, it is suitable for this projection type display apparatusto be provided with a judgment means for distinguishing an aspect ratioof projected video of the input video signal and a control means forcontrolling the adjustment means in accordance with an aspect ratiodistinguished by the judgment means.

Further, it is suitable for the projection type display apparatus tohave a screen in elliptical shape.

In this projection type display apparatus, since a screen becomestransparent when not used, a user's awareness of a screen becomes lower.Then, by making a screen elliptical in shape, the safety can be enhancedwhen not used (even if a user touches a screen without notice, a usercan not be injured, because of no-corners therein).

Furthermore, in case a screen is made elliptical-shaped as describedabove, an area where the video is not projected occurs surrounding asquare shaped area where the video is projected and the area withoutprojected video is changed according to an aspect ratio of the projectedvideo; however, when an aspect ratio of the projected video isdistinguished and the size of projected video onto a screen is adjustedin accordance with this aspect ratio, video having a various aspectratios can be projected onto an elliptical screen at a maximum angle ofview, respectively.

Furthermore, for example, it is more suitable for a screen to have anecliptic shape in which the ratio of a major axis to a minor axis isapproximately 1.3 to 1.7. Within the range, conventional video havingvarious aspect ratios (video of NTSC/PAL system with an aspect ratio of4:3, video of Hi-Vision system with an aspect ratio of 16:9, video ofCinemascope and so on) can be projected with a minimum percentage ofunused area where none of those videos are projected in anelliptical-shaped screen.

Further, in this projection type display apparatus, for example, anelectrode is provided with a liquid crystal panel constituting a screenso that the area where video is projected is distinguished from the areawhere video is not projected, and when video is projected, it issuitable for light to be dispersed only in the area where video isprojected of a liquid crystal panel by means of an electrode voltagecontrol means that controls a voltage applied to this electrode.

Accordingly, when video is projected, the area where the video is notprojected at a screen becomes a light-transmitting state (transparent).Therefore, the video can be displayed as floating in the air (withoutmaking a user conscious of the presence of the screen).

Moreover, it is suitable for a liquid crystal panel constituting ascreen to be the one using high polymer dispersion liquid crystal thatdisperses light when a voltage is applied, and that transmits light whena voltage is not applied.

Accordingly, when video is not projected, the screen becomes transparentwithout applying a voltage, a consumption of the stand-by power can bereduced when the apparatus is not used.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing an outer appearance of a videodisplay apparatus according to the present invention;

FIG. 2 is a view showing a cross-sectional structure of a screen of FIG.1;

FIGS. 3A and 3B are views showing a composition and characteristic of aliquid crystal layer of FIG. 2;

FIGS. 4A and 4B are views showing an arrangement and a shape ofrespective ITO electrodes in ITO electrode groups on a glass substrateof FIG. 2;

FIGS. 5A to 5C are views showing the range in which ITO electrodes inITO electrode groups on two glass substrates of FIG. 2 are lapped over;

FIG. 6 is a view showing a basic construction of the optical system ofan apparatus body of FIG. 1;

FIG. 7 is a block diagram showing a part of a circuit composition of anapparatus body of FIG. 1, which is relevant to the present invention;

FIG. 8 shows a table in a ROM of FIG. 7;

FIGS. 9A to 9C are views each showing the range in a screen of FIG. 1,where video is projected in accordance with a content in the table ofFIG. 8;

FIG. 10 is a view showing an unused area in a screen of FIG. 1, wherevideo is not projected;

FIG. 11 is a table showing relations between values of a, b and p offormulas {circle around (1)} and {circle around (2)}, and S1 of formula{circle around (3)} corresponding to those values and a calculationresult of an area of the whole screen;

FIG. 12 is a table showing relations between values of a, b and p offormulas {circle around (1)} and {circle around (2)}, and S1 of formula{circle around (3)} corresponding to those values and a calculationresult of an area of the whole screen;

FIG. 13 shows a table in a ROM of FIG. 7;

FIG. 14 is a flow chart showing a zoom ratio control and a screen driveprocessing performed by a CPU of FIG. 7; and

FIG. 15 is a table showing a modified example of a table of FIG. 13.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will specifically be explainedreferring to the drawings.

FIG. 1 shows an outer appearance of a video projection apparatusaccording to the present invention. In the video projection apparatus, ascreen 1 and a mirror 3 which reflects light projected from an apparatusbody 2 onto the screen 1 are attached to the apparatus body 2.

The screen 1 is elliptical in shape, and the ratio of the length of aminor axis to that of a major axis is in the range of 1.3 to 1.7 by thereason which is mentioned later.

The screen 1 is composed of a liquid crystal panel usingpolymer-dispersed liquid crystal. FIG. 2 shows a cross sectionalstructure of the screen 1. Between an ITO electrode group 13 which iscomposed of a plurality of ITO electrodes formed on a glass substrate 11through PET material 12 and an ITO electrode group 16 which is composedof a plurality of ITO electrodes formed on a glass substrate 14 throughPET material 15, a liquid crystal layer 17 having the thickness of aboutseveral ten micron is held. The liquid crystal panel used for the screen1 is composed of the ITO electrode group 13, liquid crystal layer 17,and ITO electrode group 16; and the ITO electrode groups 13 and 16 areformed in the directions of intersecting each other (at right angles).

FIGS. 3A and 3B show a composition and characteristic of the liquidcrystal layer 17. The liquid crystal layer 17 is a compound substance ofpolymer material 18 and dispersion-type liquid crystal molecules 19, andas shown in FIG. 3A, when a voltage is not applied, thelight-transmissivity becomes high (becomes transparent) with thedispersion-type liquid crystal molecules 19 being aligned, on the otherhand, as shown in FIG. 3B, when a voltage is applied, light is dispersed(becomes opaque).

As described above, contrary to conventional polymer-dispersed liquidcrystal (that disperses light when a voltage is not applied to, andtransmits light when a voltage is applied to), the liquid crystal panelconstituting the screen 1 employs polymer-dispersed liquid crystal thatdisperses light when a voltage is applied to and transmits light when avoltage is not applied to.

Note that, such polymer-dispersed liquid crystal that disperses lightwhen a voltage is applied to and transmits light when a voltage is notapplied to, is introduced at page 392 in Appl. Phys. Lett. 60 (3) issuedon Jan. 21, 1992, for example.

FIGS. 4A and 4B show arrangement and shape of each ITO electrode in theITO electrode group 13 on the glass substrate 11 and those of each ITOelectrode in the ITO electrode group 16 on the glass substrate 14,respectively. As shown in FIG. 4A, in the ITO electrode group 13, pairsof ITO electrodes 13(1), ITO electrodes 13(2), and ITO electrodes 13(3)are arranged in order from the far end symmetrically with respect to themajor axis of an ellipse of the screen 1, and an ITO electrode 13(4) isarranged in the remaining region.

As shown in FIG. 4B, in the ITO electrode group 16, pairs of ITOelectrodes 16(1), ITO electrodes 16(2), and ITO electrodes 16(3) arearranged in order from the far end symmetrically with respect to theminor axis of an ellipse of the screen 1, and an ITO electrode 16(4) isarranged in the remaining region.

FIGS. 5A to 5C each show the range in which respective ITO electrodes inthe ITO electrode group 13 and respective ITO electrodes in the ITOelectrode group 16 are lapped over on the screen 1. As shown in FIG. 5A,the range of the ITO electrodes 13(2) through 13(4) and the ITOelectrode 16(4) lapped over is a square in which the ratio of ahorizontal length and a vertical length is 4:3 with four corners thereofpositioned on the circumference of an ellipse.

As shown in FIG. 5B, the range in which the ITO electrodes 13(3) and13(4), and the ITO electrode 16(4) are lapped over is a square in whichthe ratio of a horizontal length and a vertical length is 16:9 with fourcorners thereof positioned on the circumference of an ellipse.

As shown in FIG. 5C, the range in which the ITO electrode 13(4) and theITO electrodes 16(2) through 16(4) are lapped over is a square in whicha horizontal length and a vertical length is 2.35:1 with four cornersthereof positioned on the circumference of an ellipse.

The apparatus body 2 in FIG. 1 is a three-panel transmissive type liquidcrystal projector. FIG. 6 shows a basic construction of an opticalsystem of the apparatus body 2. Light emitted from a UHP lamp (highpressure mercury lamp) 21 is made to be parallel by a reflector 22 andenters a dichroic-mirror 23.

Red light in the light entered the dichroic-mirror 23 is reflected bythe dichroic-mirror 23, and reflected by a mirror 24 to be irradiated toa liquid crystal panel 28(R).

Further, green light in the light entered the dichroic-mirror 23 istransmitted by the dichroic-mirror 23, reflected by a dichroic-mirror25, and then is irradiated to a liquid crystal panel 28(G).

Further, blue light in the light entered the dichroic-mirror 23 istransmitted by the dichroic-mirrors 23 and 25 respectively, andreflected by mirrors 26 and 27 respectively, then irradiated to a liquidcrystal panel 28 (B).

Then, red light, green light, and blue light which are modulated inaccordance with the video signal of R, G, and B, respectively at aliquid crystal panel 28(R), 28(G), and 28(B) are combined at adichroic-mirror 29 to be emitted from a projection lens 30, and thenprojected onto the screen 1 through the mirror 3.

FIG. 7 shows a part of circuit configuration of the apparatus body 2relevant to the present invention (circuits and others which drive aliquid crystal panel 28(R), 28(G), 28(B), and the like in FIG. 6 are notexplained).

A CPU 31, a ROM 32, a RAM 33, a EPROM 34 and an input-output port 35 areconnected to each other through a bus 36. To the input-output port 35,an aspect ratio judgment circuit 37, a screen drive circuit 38, anamplifier circuit 39, a group of control keys of a control panel 40 (notshown in FIG. 1) on the surface of the apparatus body 2, and a displayare connected.

The aspect ratio judgment circuit 37 distinguishes an aspect ratio ofthe video signals input to the apparatus body 2 from outside andsupplies the signal showing the judgment result to the CPU 31 throughthe input-output port 35 and the bus 36.

The screen drive circuit 38 supplies a drive voltage to respective ITOelectrodes in the ITO electrode groups 13 and 16 (FIG. 2, FIG. 4) of thescreen 1 (FIG. 1) based upon a control signal supplied from the CPU 31through the bus 36 and input-output port 35.

A stepping motor 41 that is a zoom mechanism of the projection lens 30(FIG. 6) is connected to the amplifier circuit 39.

The CPU 31 controls respective parts of the projection type displayapparatus by executing a program stored in the ROM 32. Programs of zoomratio control and a screen drive processing as shown in later describedFIG. 14 are also included in the ROM 32.

Also, a table (zoom ratio table) in which an aspect ratio of a videosignal is made to correspond to data of a zoom ratio of the projectionlens 30, and a table (drive voltage table) in which the aspect ratio ofthe video signal is made to correspond to a drive voltage of respectiveITO electrodes of the ITO electrode groups 13 and 16 of the screen 1,are stored in the ROM 32.

FIG. 8 shows contents of the zoom ratio table in the ROM 32. Also, FIG.9A to 9C each show the ranges in the screen 1, where video is projectedaccording to a content of the zoom ratio table.

As shown in FIG. 8, a zoom ratio A (A is a constant) corresponds to anaspect ratio of 4:3 (aspect ratio of NTSC/PAL system), and the amount ofzoom 1.17A corresponds to an aspect ratio of 16:9 (aspect ratio ofHi-Vision system) and the amount of zoom 1.31A corresponds to an aspectratio of 2.35:1 (aspect ratio of Cinemascope system) As shown in FIG.9A, the zoom ratio A is a value, with which four corners of video havingthe aspect ratio of 4:3 projected onto a screen 1 are exactly positionedon the circumference of an ellipse thereof (namely, the video isprojected in the range where ITO electrodes 13(2) to 13(4), and the ITOelectrode 16(4) are exactly lapped over, as shown in FIG. 5A).

When the zoom ratio A is the above value, in the zoom ratio of 1.17A, asshown in FIG. 9B, four corners of the video having the aspect ratio of16:9 projected onto the screen 1 are exactly positioned on thecircumference of an ellipse thereof (namely, the video is projected inthe range where ITO electrodes 13(3) and 13(4), and ITO electrodes 16(3)and 16(4) are exactly lapped over, as shown in FIG. 5B), and in the zoomratio 1.31A, as shown in FIG. 9C, four corners of the video having theaspect ratio of 2.35:1 projected onto the screen 1 are exactlypositioned on the circumference of an ellipse thereof (namely, the videois projected in the range where an ITO electrode 13(4), and ITOelectrodes 16(2) to 16(4) are exactly lapped over, as shown FIG. 5C).

As described above, when four corners of video rojected onto the screen1 are located on the circumference of an ellipse thereof, the video isprojected onto the screen 1 at the maximum angle of view. However, inorder to position four corners of video having the aspect ratio of 4:3on the circumference of an ellipse of the screen 1, each length of themajor and minor axes of an ellipse of the screen 1 is set to a and brespectively, each of the vertical and horizontal lengths of theprojected video is set as 3k and 4k, respectively (though k is aconstant, here, k=1 as a matter of convenience), and the followingformula {circle around (1)} must be satisfied.4² /a ²+3² /b ²=1   {circle around (1)}

Also, in order to position four corners of video having an aspect ratioAr (Ar is a ratio other than 4:3) on the circumference of an ellipse ofthe screen 1, the horizontal length of the video projected onto thescreen 1 is set to p·k (here, also k=1), and the following formula{circle around (2)} must be satisfied.p ^(2/) a ²⁺⁽ p×Ar)² /b ²=1  {circle around (2)}

Then, in case of projecting the video having the aspect ratio of 4:3 andthe video having the aspect ratio of Ar onto a screen 1 such that fourcorners thereof are respectively positioned on the circumference of anellipse of the screen 1, the shaded area specified in the screen 1 ofFIG. 10 is an unused area where none of the video is projected. An areaS1 of the area where video is not projected is shown by the followingformula {circle around (3)}.S1=π×a×b−(4×3)×4−(p−4)×Ar×p×4  {circle around (3)}

FIG. 11 shows, when the aspect ratio Ar is set to 16:9 (the aspect ratioof Hi-Vision system), relationships between values of a, b, and p thatsatisfy above formulas {circle around (1)}, {circle around (2)}, and thecalculation results of an area S1 and the whole area of screen 1 witha/b (a ratio of a length of major axis to a length of minor axis of anellipse of screen 1) being within the range from 1.3 to 1.7.

When a/b is in the range from 1.3 to 1.7, the calculation result isobtained that the ratio of an area S1 (an area onto which both the videoof an aspect ratio of 4:3 and the video of an aspect ratio of 16:9 arenot projected) to the whole area of screen 1 becomes small compared tothe case in which a/b is not in this range.

Further, FIG. 12 shows, when the aspect ratio Ar is set to 2.35:1 (anaspect ratio of Cinemascope system), relationships between values of a,b, and p that satisfy above formulas {circle around (1)}, {circle around(2)}, and the calculation result of an area S1 and the whole area ofscreen 1 with a/b (a ratio of a length of major axis to a length ofminor axis of an ellipse of screen 1) being within the range from 1.3 to1.7.

When a/b is in the range from 1.3 to 1.7, the calculation result isobtained that the ratio of an area S1 (an area onto which both the videoof an aspect ratio of 4:3 and the video of an aspect ratio of 2.35:1 arenot projected) to the whole area of screen 1 becomes small compared tothe case in which a/b is not in this range.

As described above, when a/b (a ratio of the length of major axis to thelength of minor axis of an ellipse of screen 1) is set within the rangefrom 1.3 to 1.7, a ratio of unused area, where none of the video isprojected, to the whole screen could be small. By that reason, the ratioof the length of minor axis to the length of major axis is set withinthe range from 1.3 to 1.7.

FIG. 13 shows contents of a table of drive voltage in the aforementionedROM 32. To the aspect ratio of 4:3 (an aspect ratio of NTSC/PAL system)a drive voltage corresponds, in which a voltage is applied between ITOelectrodes 13(2) to 13(4) in the ITO electrode group 13 and ITOelectrode 16(4) in the ITO electrode group 16; and between ITO electrode13(1) in the ITO electrode group 13 and ITO electrodes 16(1) to 16(3) inthe ITO electrode group 16 (ITO electrodes 13(2) to 13(4) have equalelectric potential to ITO electrodes 16(1) to 16(3), and are furtherequal to electric potential ITO electrode 13(1) and ITO electrode16(4)).

This drive voltage is such voltage that causes only an area where ITOelectrodes 13(2) to 13(4) and ITO electrode 16(4) are lapped over to beopaque (FIG. 5A), and that causes the remaining part to be transparent,with respect to the screen 1.

To the aspect ratio of 16:9 (an aspect ratio of Hi-Vision system), adrive voltage corresponds, in which a voltage is applied between ITOelectrodes 13(3) and 13(4) in the ITO electrode group 13 and ITOelectrodes 16(3) and 16(4) in the ITO electrode group 16; and betweenITO electrodes 13(1) and 13(2) in the ITO electrode group 13 and ITOelectrodes 16(1) and 16(2) in the ITO electrode group 16 (ITO electrodes13(3) and 13(4) have equal electric potential to ITO electrodes 16(1)and 16(2), and are further equal to the electric potential of ITOelectrode 13(1) and 13(2), and ITO electrodes 16(3) and 16(4)).

This drive voltage is such voltage that causes only an area where ITOelectrodes 13(3) and 13(4), and ITO electrodes 16(3) and 16(4) arelapped over to be opaque (FIG. 5B), and causes the remaining part to betransparent, with respect to the screen 1.

To the aspect ratio of 2.35:1 (an aspect ratio of Cinemascope system), adrive voltage corresponds, in which a voltage is applied between ITOelectrode 13(4) in the ITO electrode group 13 and ITO electrodes 16(2)to 16(4) in the ITO electrode group 16; and between ITO electrodes 13(1)to 13(3) in the ITO electrode group 13 and ITO electrode 16(1) in theITO electrode group 16 (ITO electrode 13(4) has equal electric potentialto ITO electrode 16(1), and is further equal to the electric potentialof ITO electrodes 13(1) to 13(3) and ITO electrodes 16(2) to(4)).

This drive voltage is such voltage that causes only an area where ITOelectrode 13(4) and ITO electrodes 16(2) to 16(4) are lapped over to beopaque (FIG. 5C), and causes the remaining part to be transparent, withrespect to the screen 1.

In FIG. 7, various types of data generated in the process of the CPU 31executing a program in the ROM 32 are temporally stored in the RAM 33.Data indicating the present position of the stepping motor 41 is storedin the EPROM 34.

FIG. 14 is a flow chart showing zoom ratio control and screen driveprocessing performed by the CPU 31. This processing starts, when asignal indicating a judgment result of an aspect ratio is transmittedfrom the aspect ratio judgment circuit 37; and first, referring to thetable of a zoom ratio in the ROM 32 (FIG. 8), and a zoom ratiocorresponding to the aspect ratio distinguished by the aspect ratiojudgment circuit 37 is decided as the zoom ratio of the projection lens30 (Step S1).

Next, based upon the data of present position of the stepping motor 41in the EPROM 34 a and the zoom ratio decided in Step 1, an amount ofrelative displacement of the stepping motor 41 to make the projectionlens 30 have this decided zoom ratio is calculated (Step S2).

Further, a control signal which makes the stepping motor 41 move only bythe amount of relative displacement calculated at Step S2, is suppliedto the stepping motor 41 through the bus 36, input-output port 35, andamplifier circuit 39 (Step S3).

Subsequently, referring to the table of drive voltage in the ROM 32(FIG. 13), a drive voltage corresponding to the aspect ratiodistinguished by the aspect ratio judgment circuit 37 is decided as adrive voltage of the screen 1 (Step S4).

Then, a control signal which causes the decided drive voltage to besupplied to respective ITO electrodes of the ITO electrode groups 13 and16 (FIG. 2, FIG. 4) of the screen 1 (FIG. 1) is supplied to the screendrive circuit 38 through the Bus 36 and the input-output port 35 (StepS5). Then, the processing is finished.

Next, there will be explained the effectiveness of the above projectiontype display apparatus being set in comparatively small space such as athome.

The above projection type display apparatus is a front projection typedisplay apparatus (namely, the apparatus body 2 and the screen 1 areintegrally provided) in which video is projected onto a screen 1attached to the apparatus body 2 from a front side. Therefore, there isno need to install a screen on a wall or the like at home, contrary to aconventional front projection type display apparatus. Also, beingdifferent from a conventional rear projection type display apparatus,since the part of optical pass from a projection lens to a screen (partof the optical pass from the projection lens 30 of FIG. 6 to the mirror3 and screen 1 of FIG. 1) is not contained in the housing, the apparatuscan be small-sized. Accordingly, for example at home, the apparatus canbe put on a table and can be brought to another room, so that a placefor setting the apparatus can more freely be selected.

Further, in this projection type display apparatus the screen 1 iscomposed of a liquid crystal panel using polymer-dispersed liquidcrystal. The screen 1 can be made to be in the state of dispersing light(opaque) for projecting video, and to be in the state of transmittinglight (transparent) when the video is not projected (when the projectiontype display apparatus is not used) so that the screen is notconspicuous. Accordingly, the screen shall not be conspicuous contraryto a conventional projection type display apparatus, when not used.Further, as described above, this projection type display apparatus issmaller in size than a rear projection type display apparatus. By thisreason, for example at home, a feeling of uncomfortable oppression isnot given to the living environment when the apparatus is not used.

Furthermore, the liquid crystal panel constituting the screen 1 usespolymer-dispersed liquid crystal that disperses light when a voltage isapplied, and that transmits light when a voltage is not applied.Therefore, when video is not projected, the screen 1 can be transparentwithout applying a voltage, so that a consumption of standby power canbe reduced when the apparatus is not used.

Furthermore, in this projection type display apparatus, the awareness ofa user about the screen becomes lower, because the screen 1 istransparent when not used; however, since the screen 1 iselliptical-shaped, the safety is enhanced when the apparatus is not used(even if a user touches a screen without notice, the user can not beinjured, because of no-corners therein).

Subsequently, the operation and effectiveness of this projection typedisplay apparatus, when video is projected, will be explained.

When the video signal having an aspect ratio of 4:3 (NTSC/PAL system) isinput into the apparatus body 2 of this projection type displayapparatus, since the aspect ratio of 4:3 is distinguished in the aspectratio judgment circuit 37 (FIG. 7), with the zoom ratio control andscreen drive processing (FIG. 14) of the CPU 31 (FIG. 7) the video isprojected onto the screen 1, as shown in FIG. 9A, such that four cornersof the video having aspect ratio of 4:3 are exactly positioned on thecircumference of an ellipse of the screen 1 (specifically, the video isprojected onto the range where ITO electrodes 13(2) to 13(4) and ITOelectrode 16(4) of FIG. 5A are lapped over), and a drive voltage, whichcauses only the above range of ITO electrodes 13(2) to 13(4) and ITOelectrode 16(4) being lapped over to be opaque, is supplied to thescreen 1.

Therefore, since a part where the video is projected onto the screen 1(the range where ITO electrodes 13(2) to 13(4) and ITO electrode 16(4)are lapped over) becomes opaque, the video can be seen from a front sideof the screen 1 and also, a part where the video is not projected of thescreen 1 remains transparent.

On the other hand, when the video signal having an aspect ratio of 16:9(Hi-Vision system) is input into the apparatus body 2 of this projectiontype display apparatus, since the aspect ratio of 16:9 is distinguishedin the aspect ratio judgment circuit 37, with the zoom ratio control andscreen drive processing of the CPU 31 the video is projected onto thescreen 1, as shown in FIG. 9B, such that four corners of the videohaving aspect ratio of 16:9 are exactly positioned on the circumferenceof an ellipse of the screen 1 (specifically, the video is projected ontothe range where ITO electrodes 13(3) and 13(4), and ITO electrodes 16(3)and 16(4) of FIG. 5B are lapped over), and a drive voltage, which causesonly the above range of ITO electrodes 13(3) and 13(4) and ITOelectrodes 16(3) and 16(4) being lapped over to be opaque, is suppliedto the screen 1.

Therefore, since an area where the video is projected onto the screen 1(the range where ITO electrodes 13(3) and 13(4), and ITO electrode 16(3)and 16(4) are lapped over) becomes opaque, the video can be seen from afront side of the screen 1 and also, a part where the video is notprojected of the screen 1 remains transparent.

On the other hand, when the video signal having an aspect ratio of2.35:1 (Cinemascope) is input into the apparatus body 2 of thisprojection type display apparatus, since the aspect ratio of 2.35:1 isdistinguished in the aspect ratio judgment circuit 37, with the zoomratio control and screen drive processing of the CPU 31 the video isprojected onto the screen 1, as shown in FIG. 9C, such that four cornersof the video having aspect ratio of 2.35:1 are exactly positioned on thecircumference of an ellipse of the screen 1 (specifically, the video isprojected onto the range where ITO electrodes 13(4) and ITO electrodes16(2) to 16(4) of FIG. 5C are lapped over), and a drive voltage, whichcauses only the above range of ITO electrode 13(4) and ITO electrodes16(2) to 16(4) being lapped over to be opaque, is supplied to the screen1.

Therefore, since an area where the video is projected onto the screen 1(the range where ITO electrode 13(4) and ITO electrodes 16(2) to 16(4)are lapped over) becomes opaque, the video can be seen from a front sideof the screen 1 and also, a part where the video is not projected of thescreen 1 remains transparent.

As described above, when any one of videos having the aspect ratio of4:3 (NTSC/PAL system), aspect ratio of 16:9 (Hi-Vision system), andaspect ratio of 2.35:1 (Cinemascope system) is projected, four cornersof the video projected onto the screen 1 are exactly located on thecircumference of an ellipse thereof, so that the video is projected ontoa screen 1 with the maximum angle of view.

Further, since the ratio of the length of major axis to the length ofminor axis is set within the range of 1.3 to 1.7, the proportion of anunused area, where none of the videos of the aspect ratio of 4:3, of theaspect ratio of 16:9, and of the aspect ratio 2.35:1 (Cinemascope) isprojected, to the whole area of the screen 1, becomes as small aspossible, as shown in FIGS. 11 and 12.

Moreover, ITO electrodes 13(1) through 13(4) and ITO electrodes 16(1)through 16(4) are provided with a liquid crystal panel constituting thescreen 1 to distinguish an area where video is projected and an areawhere the video is not projected, and when any one of videos of theaspect ratio of 4:3, of the aspect ratio of 16:9, and of the aspectratio of 2.35:1 (Cinemascope system) is projected, the part of thescreen 1, where the video is not projected, remains transparent.Therefore, display can be performed such that the video is floating inthe air (without a user being conscious of the presence of the screen1).

Note that, in the above embodiments, a table in the ROM 32, ITOelectrode groups 13 and 16 of a liquid crystal panel constituting thescreen 1, and a zoom ratio control and screen drive processing of theCPU 31 correspond to the three aspect ratios of 4:3, 16:9, and 2.35:1.However, the present invention is not limited thereto, and those tables,ITO electrode groups 13 and 16, and the processing may correspond toaspect ratios other than those of 4:3, 16:9, and 2.35:1 (for example,corresponds to an aspect ratio of 1.85 (American-Vista)).

Further, in the above embodiments, in the zoom ratio control and screendrive processing of the CPU 31 the zoom ratio is decided uniquely by thejudgment result of the aspect ratio judgment circuit 37. However, asanother embodiment, there may be the case in which when a user performsan operation of specifying a zoom ratio with a control panel 40, thespecified zoom ratio is given priority.

Furthermore, in the above embodiments, the case in which the screen 1 iselliptical in shape is mentioned; however, the outer appearance of thescreen 1 is not limited thereto, and the preset invention can be appliedto various shapes. In the predetermined shape of screen regardless ofrectangular or circular, the area where video is not projected ischanged according to an aspect ratio of the video to be projected.Accordingly, by adjusting a size of the video projected onto a screen inaccordance with the aspect ratio, videos with various aspect ratios canbe projected onto a predetermined shaped screen with the maximum angleof view, respectively.

Further, in the above embodiments, a liquid crystal panel constitutingthe screen 1 uses polymer-dispersed liquid crystal that disperses lightwhen a voltage is applied, and that transmits light when a voltage isnot applied. However, as another embodiment, a conventionalpolymer-dispersed liquid crystal (that disperses light when a voltage isnot applied, and transmits light when a voltage is applied) can be used.

In that case, if contents of the table of drive voltage in a ROM 32(FIG. 13) is changed into that shown in FIG. 15, when any one of videosof the aspect ratio of 4:3, of the aspect ratio of 16:9, and of theaspect ratio of 2.35:1 is projected, the part of a screen 1, where videois not projected, could also be transparent and the video can bedisplayed as floating in the air.

Further, in the above embodiments, the apparatus body 2 is a three-paneltransmissive type liquid crystal projector. However, as anotherembodiment, the apparatus body 2 may be a single-panel transmissive typeliquid crystal projector, a projector using a spatial light modulatingelement (for example, DMD (Digital Mirror Device)), or a projector usinga CRT.

Further, in the above embodiments, although the light from the apparatusbody 2 is reflected by the mirror 3 and is projected onto the screen 1,the light from an apparatus body can directly be projected onto thescreen.

Further, in the above embodiments, although the video is projected fromthe apparatus body 2 to be obtained as the diffused light on a screen 1and a user watches the video from the front side, there can be anothercase in which the user watches the video obtained as the diffused lightfrom the rear side.

Further, it is to be understood that the present invention is notlimited to the above embodiments and that various structure could betaken without departing from the spirit or scope of the presentinvention.

As described above, according to a projection type display apparatus ofthe present invention, even if the apparatus is used in a comparativelysmall space such as at home, a place for setting the apparatus can beselected more flexibly, and effectiveness of not giving a feeling ofuncomfortable oppression is obtained.

Furthermore, effectiveness of reducing the consumption of standby powercan be obtained when the apparatus is not used.

Furthermore, effectiveness of projecting videos having various aspectratios onto a screen of a predetermined shape with the maximum angle ofview can be obtained, respectively.

Furthermore, effectiveness of enhancing the safety when not used can beobtained, and the videos with various aspect ratios can be projectedonto an elliptical screen with the maximum angle of view, respectively.

Furthermore, effectiveness of projecting various videos withconventional aspect ratios (video of NTSC/PAL system with an aspectratio of 4:3, video of Hi-Vision system with an aspect ratio of 16:9,video of the Cinemascope, and so on) with a minimum percentage of unusedarea of an elliptical-shaped screen, where none of those videos areprojected, can be obtained.

Furthermore, effectiveness of displaying video such that the video isfloating in the air (without a user being conscious of the presence ofthe screen) can be obtained.

1. A projection type display apparatus that projects video onto ascreen, comprising: a liquid crystal panel using polymer-dispersedliquid crystal that disperses light when a voltage is applied and thattransmits light when a voltage is not applied, being attached to a bodyof the apparatus as a screen, wherein said liquid crystal panelcomprises: a first group of electrodes including a first predeterminednumber of electrodes; and a second group of electrodes including asecond predetermined number of electrodes; wherein said first group ofelectrodes is arranged in a direction perpendicular to a direction inwhich said second group of electrodes is arranged; wherein the videooutput from said body of the apparatus is projected onto said screenfrom the front side, and wherein each of a four corners of a pluralityof aspect ratios of video are located on the circumference of an ellipseshaped screen, a location of each of the four corners being a functionof the aspect ratio, and wherein said screen transmits light in an areaof the screen where said video is not projected.
 2. A projection typedisplay apparatus according to claim 1, wherein video is projected ontosaid screen through a mirror.
 3. A projection type display apparatusaccording to claim 1 further comprising: adjustment means for adjustingthe size of video that is projected onto said screen, and control meansfor controlling said adjustment means in accordance with an aspect ratioof the projected video.
 4. A projection type display apparatus accordingto claim 3, wherein an electrode is provided with said liquid crystalpanel to distinguish the area where video is projected from the areawhere the video is not projected, and according to the aspect ratio ofsaid video, said control means controls a voltage supplied to saidelectrode such that light is dispersed only at the area where video isprojected in said liquid crystal panel.
 5. A projection type displayapparatus according to claim 3, further comprising: judgment means fordistinguishing an aspect ratio of the video projected by input videosignals, and control means for controlling said adjustment means inaccordance with said aspect ratio distinguished by said judgment means.6. A projection type display apparatus according to claim 3, whereinsaid screen is elliptical in shape.
 7. A projection type displayapparatus according to claim 6, wherein said screen has an ellipticalshape in which the ratio of a major axis to a minor axis is within therange approximately from 1.3 to 1.7.
 8. A projection type displayapparatus according to claim 1, wherein an electrode is provided withsaid liquid crystal panel to distinguish the area where video isprojected from the area where the video is not projected, and when videois projected, light is dispersed by an electrode voltage control meansthat controls a voltage supplied to said electrode only at the areawhere the video is projected in said liquid crystal panel.
 9. Aprojection type display apparatus according to claim 8, wherein saidliquid crystal panel comprises: a liquid crystal layer, a firstelectrode that is provided on the front side of said liquid crystallayer and that consists of a plurality of areas in a predetermineddirection, and a second electrode that is provided on the rear side ofsaid liquid crystal layer and that consists of a plurality of areas in adirection perpendicular to said predetermined direction; and light isdispersed by said electrode voltage control means at said area wheresaid first electrode and said second electrode, both of which aresupplied with said voltage, are lapped over.
 10. A projection typedisplay apparatus that projects video onto a screen comprising: a liquidcrystal panel using polymer-dispersed liquid crystal, being attached toa body of apparatus as a screen, adjustment means for adjusting the sizeof video projected onto said screen, control means for controlling saidadjustment means in accordance. with an aspect ratio of the projectedvideo, wherein said liquid crystal panel comprises: a first group ofelectrodes including a first predetermined number of electrodes; and asecond group of electrodes including a second predetermined number ofelectrodes; wherein said first group of electrodes is arranged in adirection perpendicular to a direction in which said second group ofelectrodes is arranged; wherein each of a four corners of a plurality ofaspect ratios of video are located on the circumference of an ellipseshaped screen, a location of each of the four corners being a functionof the aspect ratio, and wherein when the video is projected onto thescreen, a part of the screen where said video is not projected remainstransparent.
 11. A projection type display apparatus according to claim10, further comprising: judgment means for distinguishing an aspectratio of video projected by input video signals, and control means forcontrolling said adjustment means in accordance with said aspect ratiodistinguished by said judgment means.
 12. A projection type displayapparatus according to claim 10, wherein said screen is elliptical inshape.
 13. A projection type display apparatus according to claim 12,wherein said liquid crystal panel has an elliptical shape in which aratio of a major axis to a minor axis is within the range approximatelyfrom 1.3 to 1.7.
 14. A projection type display apparatus according toclaim 10, wherein an electrode is provided with said liquid crystalpanel to distinguish the area where video is projected from the areawhere the video is not projected, and when video is projected, light isdispersed by an electrode voltage control means that controls a voltagesupplied to said electrode only at the area where the video is projectedin said liquid crystal panel.
 15. A projection type display apparatusaccording to claim 14, wherein said liquid crystal panel comprises: aliquid crystal layer, a first electrode that is provided on the frontside of said liquid crystal layer and that consists of a plurality ofareas in a predetermined direction, and a second electrode that isprovided on the rear side of said liquid crystal layer and that consistsof a plurality of areas in a direction perpendicular to saidpredetermined direction; and light is dispersed by said electrodevoltage control means at said area where said first electrode and saidsecond electrode, both of which are supplied with said voltage, arelapped over.
 16. A projection type display apparatus according to claim10, wherein said liquid crystal panel uses polymer-dispersed liquidcrystal that disperses light when a voltage is applied and thattransmits light when a voltage is not applied.